442 
CONCHIFERA. 
Chama Lazarus. — The Lazarus’s Cham a. 
Plate LXXXVIII. fig. 20. 
With imbricated, dilated, waved foliations, and obsoletely 
striated ; of a white, orange, red, or yellow colour; white 
within. Two inches in diameter. Inhabits the American seas. 
Genus 3.—DICER AS.— Lamarck. 
Generic Character. —Inequivalve, adherent; beaks conical, 
very large, diverging in irregular, spiral contortions ; hinge with 
a large, thick, concave, subauricular tooth in the larger promi¬ 
nent valve ; two muscular impressions. 
Diceras arietina. — The Ram-Horned Diceras. 
Plate LXXXIX. fig. 7. 
Somewhat heart-shaped, with divergent beaks. Fossil. 
Section II— Lamellipedes. —The foot depressed, lamelli- 
form, and not posterior. 
TRIBE I.-NAYADES. 
Shells inhabiting fresh waters ; the hinge sometimes having 
an irregular, simple, or cleft tooth, and a longitudinal, prolonged 
one, and sometimes none ; some have irregular, granulated tu¬ 
bercles, the whole length of the upper part; a compound mus¬ 
cular impression ; and the umbo oftentimes decorticated. 
Genus 4.—IRIDINA.— Lamarck. 
Generic Character. —Equi valve, inequilateral, transverse; 
beaks small, turned to one side and nearly straight; two separ¬ 
ate lateral, muscular impressions ; hinge long, linear, and atten¬ 
uated near the centre, tuberculous and nearly crenated ; tubercles 
unequal; ligament external and marginal. 
Iridina Nilotica. — The Nile Iridina. 
Plate LXXXVIII. fig. 22. 
Shell transversely oblong ; dark olivaceous green on the out¬ 
side, somewhat wrinkled, concentrically; inside, fine pearly, 
with iridescent reflections. Five inches long. Inhabits the 
Nile. 
